1. Field of the Invention
This invention relates to bituminous surfacing compositions and more particularly to compositions for use in paving construction, which compositions utilize bituminous emulsions prepared using an alkoxylated asphalt as the emulsifying agent.
2. Description of the Prior Art
Bitumen or asphalt is widely used for many applications with paving and surface coating possibly being the most extensive. While asphalt may be applied by different methods, there has been an increasing shift the emulsions, both cationic and anionic to replace cutbacks and hot asphalt in many applications. Cationic emulsions are obtained by dispersing fine asphalt particles in a continuous water phase by use of cationic emulsifiers. The emulsion particles carry a positive charge and readily deposit or coat the aggregate which is generally negatively charged. The rate of asphalt deposition may be varied somewhat by the emulsifier and emulsion formulation used but is relatively rapid compared to anionic emulsions which depend more upon evaporation of water for their deposition. In unstabilized emulsions, the deposition of asphalt may take place immediately upon contact with the aggregate which usually results in the asphalt being deposited upon the aggregate in large droplets without the aggregate being completely or uniformaly coated. Stabilizers are often added to the emulsions to control the set to permit substantially uniform and complete coating of the aggregate with a continuous asphalt film.
The use of spent sulfite liquor or lignosulfonate as an anionic asphalt emulsifier, as well as the use of ammonium lignosulfonate have been disclosed in U.S. Pat. Nos. 2,332,542 and 2,494,708. Calcium lignosulfonate in U.S. Pat. No. 2,978,342 has been suggested as an anti-stripping agent for use in hot asphalt applications to enhance the coating and bonding of the hot asphalt to wet aggregate such that it will not readily be displaced or stripped from the aggregate upon being subjected to water. However, in cationic asphalt emulsions, spent sulfite liquor or lignosulfonate is not sufficiently compatible or effective as a stabilizer to be used to any extent. The reaction of alkali lignins with primary and secondary amines and formaldehyde in the Mannich-type reaction has been disclosed for the preparation of a cationic asphalt emulsifier in U.S. Pat. No. 3,126,350 as well as disclosure made in U.S. Pat. No. 3,718,639 that lignin base asphalt emulsion additives may be obtained by reacting alkali lignin with a tertiary amineepichlorohydrin intermediate condensation product. The latter processes involve costly processing and a stabilizer which could be prepared more simply from lignin is greatly desired.
It is an object of this invention to provide a bituminous emulsion and a bituminous emulsion-mineral aggregate composition wherein in the said emulsion, the emulsifier is an alkoxylated asphalt.